Question

when two heterozygous parents are crossed (aa x aa), what percent of the offspring will have a dominant phenotype? a 100% b 50% c 75% d 25%

Explanation:

Step1: Set up Punnett square

Parents: \(Aa\times Aa\)

	A	a
a	Aa	aa

Step2: Determine genotypes and phenotypes

Genotypes: \(AA:Aa:aa = 1:2:1\)
Phenotype: \(AA\) and \(Aa\) show dominant phenotype.

Step3: Calculate percentage

Number of dominant - phenotype offspring (\(AA + Aa\)): \(1 + 2=3\)
Total offspring: \(4\)
Percentage: \(\frac{3}{4}\times100\% = 75\%\)

Answer:

C. 75%